Land vehicles and earthworking vehicles, in particular, are, during operation, subject to extreme vibrational forces which are a source of considerable discomfort to the operator. Also, operator protection standards are provided by law which limit the noise level to which operators can be exposed. Because sound and other vibrations are readily transmitted through metal-to-metal contact, the utility of a resilient mounting system for securing the cab to the vehicle becomes apparent. The use of a cushioned mounting system for land vehicles has been explored in prior patents, those among the most pertinent being Utz et al U.S. Pat. No. 2,144,170, issued Jan. 17, 1939; Schaldenbrand U.S. Pat. No. 2,838,339, issued June 10, 1958; and Palmer U.S. Pat No. 3,990,737, issued Nov. 9, 1976.
Both the Utz et al and Schaldenbrand patents contemplate the use of a pair of apertured resilient insulators or mounts encasing a bolt which secures a body to a frame, the insulators being compressed when the mount is fully assembled. The Utz et al patent further envisions the degree of hardness of the resilient members being varied to provide the required relative movement between the body and the chassis. The Palmer patent, which has the same assignee as the present invention, discloses a mounting system wherein a rubber-like base pad is placed between the vehicle and the cab and the bolts securing the cab to the vehicle are encased with a resilient bushing. Palmer allows strong metal-to-metal contact to occur in the event of a large force, such as the vehicle overturning.